The activation of C-Cl bonds in dichloromethane and chloroform was observed by BeCl2 in the presence of PMe3 and PCy3. This leads to the formation of [Me3PCH2Cl]Cl and [Cy3PCHCl2][BeCl3]. The latter compound is the first example of a tricoordinated beryllium species with nonbulky ligands and proof of the existence and stability of the long-predicted [BeCl3](-) ion. In analogy to the isoelectronic BCl3, the trichloroberyllate anion exhibits Lewis acidic behavior toward electron-pair donors and was probed for the electronic and steric influence of the Lewis base. [BeCl3](-) can also act as a chloride ion donor or acceptor, leading to the formation of neutral phosphane adducts to BeCl2 and [BeCl4](2-). The existing equilibria between these species were investigated and showed high chloride mobility.